使用SQL使用多个查询的多个SQL计数

Question

我需要做多次计数。我有大约6列。像这样：

SELECT 
COUNT(C.ID) as 'Column 1',
COUNT(C.ID) as 'Column 2',
COUNT(C.ID) as 'Column 3',
COUNT(C.ID) as 'Column 4',
FROM CONTACT C

我需要能够使用不同的查询运行不同的计数，但不确定如何在一个结果中应用查询计数。

Answer 1

这里有几种选择。

1）使用子查询作为@TheSoultion提议

2）使用UNION

   SELECT 'A' NAME, COUNT(c.ID) [COUNT] FROM Contact c WHERE ... 
   UNION
   SELECT 'B' NAME, COUNT(c.ID) [COUNT] FROM Contact c WHERE ... 

3）如果它实际上是相同的子集但你想根据某些条件求和，那么在你的计数内使用用例

 SELECT sum(case ... when ... then 1 else 0 end) counta,
        sum(case ... when ... then 1 else 0 end) countb
 FROM ... WHERE ...

Answer 2

如果我理解你要做的事情，我通常会这样做：

SELECT 
SUM(CASE WHEN Condition1 THEN 1 END) AS Column1,
SUM(CASE WHEN Condition2 THEN 1 END) AS Column2
FROM Contact

Answer 3

您需要运行子查询，或者至少是单向运行：

SELECT
    ( SELECT COUNT(c.ID) FROM Contact c WHERE ... ) AS Column1,
    ( SELECT COUNT(c.ID) FROM Contact c WHERE ... ) AS Column2